We study the dynamics of cell resistance and the filament stability in SiO2-based electrochemical metallization memories (ECM) by electrochemical impedance spectroscopy (EIS). We discuss the influence of the frequency range and amplitude. The effect of applied DC voltage pulses on the (in)stability and behaviour of the filament is reported. Even small voltages of 10 mV can change the cell resistance. Our aim to understand the cell dynamics at conditions close to the quantum point contact where only few atoms may be responsible for the direction of the process towards stabilization of the LRS state or its transition to HRS.